Vacuum distillation and rectification of paraffin distillate



Feb. 4, 1930. N. E. Looms r AL VACUUM DIS'IILLATIQN AND RECTIFICATION OF PARAFFIN DISTILLATE Filed June 1924 Y F7LTE/Z PRESS f f f 'i. Q 7 .g'uvcnlbli Nnthuiel E Loomis an 'Waurren L CwiS.

Patented Feb. 4, 1930 UNITED STATES PATENT oFFicE NATHANIEL E. LOQMIS, OF ELIZABETH, NEW JERSEY, AND WARREN K. LEWIS,., OF

CAMBRIDGE, MASSACHUSETTS ASSIGNORS TO STANDARD OIL DEVELOPMENT GOM- PANY, A ('JORIIE'ORA'.I.I0N OF DELAWARE VACUUM DISTILLATION,AND RECTIFICATION OF IPARAFFIN DISTILLATE Application filed June 2, 1924; Serial No'. 717,226.

This invention relates to the preparation of hydrocarbon products, and will be understood from the following description, taken in connection with the accompanying drawmore viscous lubricating constituents are distilling over, the temperature of the still is within the cracking range, and it has-been generally believed heretofore that a certain amount of, cracking was necessary in order to secure'a high boiling point .parafiin distillate in which the wax content would be of such character as to permit of separation of the wax by chilling and filter-pressing.

By the procedure referred to, i. e., 'bywre sortlng to a mild but well defined and important cracking, it has been possible to obtain all but the very heaviest portion of the paraffin distillate asa single fraction which could be chilled and filter-pressed in the ordinary way to yield a low-cold-test lubricating distillate ready for further refining, and a slack wax of dominantly crystalline character from which, by the recognized methods of sweating and treating and decolorizing, a

crude scale or refined scale wax of merchantable quality can be made. The remainder of the paraflin carrying distillate, which might amount tothe heaviest 2Q.% thereof, is of'such characterthat it cannot be directly handled as above described. It is common to rerun this product, known as paraiiin slop, in coking stills, thus subjecting it to a second cracking, and by this means to secure the major portion of it as a distillate similar in quality to the original parafiin distillate.

' The unfit portion of the distillate resulting from this rerunning operation, i. e., the parafiin slop from paralfin slop, is remixed with method known to refiners for pro straight parafi'in slop and in this way eventually disposed of.

Where it is desired to produce primarily a viscous residual lubricating oil rather than a viscous distillate oilfrom paraflin base crude, the original'distillation must obviously be accomplished Without substantial cracking. In this case, the first portion of the parafiin distillate, i. e., the lowest boiling fraction thereof, amounting to perha s 50% of the total, is out directly as a single f ra'ction on thecrude distillation, but in the absence of the cracking referred to, the second portion, in amount up to about one-half the total is of unfit character. This unfit paraflin distillate or paraffin slop from crude distillation operations in which cracking is reduced to a minimum, is therefore large in amount.

It is commonly handled by rerunning under conditions involving well defined cracking and thus separated into a fit and an unfit portion as above described.

In the present state of the artthere is no d ucing from a paraifin bearing'cru'de oil, such as Pennsylvania or Mid-continent crude, a quality of heavy or viscous paraflin distillate which will give a viscous low-cold-test lubricating distillate and a dominantly crystalline dry wax cake by the universally used chilling and filter-pressing methods, without subjecting the heavier wax-bearing constituents of the oil .to a well defined cracking operation, either as a part of the original distillation of the crude oil or in a subsequent rerunning of the crude distillate. v

-In the accompanying drawings Fig. 1 is a diagrammatic horizontal plan of apparatus in which our method may be practiced; and

Fig. 2 is a sectional detail, showing a portion of a rectifying column.

In proceeding in accordance with the present invention, oil which contains paralfin is distilled, taking oif cuts of lighter distillate as' desired', and while substantially avoiding cracking, as for example by application of a vacuum, the lubricating constitutents are taken 0E, dissolved wax coming also therewith. By adequate rectification a heavy or viscous paraflin distillate is obtained which-.100

is readily pressable on filter presses to separate out the wax in the ordinary way, and the destruction of a part of the wax and a part of the lubricating oil by cracking as in the practice above referred to is avoided. We

have found then that the yields of products.

realized by the use of our process are mate rially greater than the yields obtained by operating under present practice. According to our new process the distillation may be carried out in batch stills if desired, raising the temperature for the successive cuts of distillate, and applying adequate fractionation and a vacuum while the parafi'in dis-- fer to employ plate columns, the plates being perforated to allow vapors to bubble through layers of accumulated liquid, and with or without bell-caps. Each tower has a final condenser, such as water-cooled condenser 8 and a receiver. From the receivers of thestills which are to be under vacuum, for example receivers 9 and 10, connections 11 lead to avacuum-producing means, as pump 12.

With the stills all heated to the respective temperatures for taking ofi" their successive a cuts, and a vacuum being applied to the stills taking off the last cuts of distillate (for illustration a vacuum-corresponding to an absolute pressure substantially equivalent to 30 mm. of mercury to allow a final-still temperature of not over 640 F.) from the earlier stills in the series there will successively come off naphtha, water white oil, etc, and from the vacuum still 2 a viscous paraflin distillate or lubricating fraction containing dissolved wax. vAs the paraffin distillate vapors pass through successive rectification zones in the tower, the constituents are progressively fractionated and the condensate obtained in the receiver 10 is available to be forwarded by a pump 13 throughv a chiller 14 to cause dissolved parafiin wax to form crystals, and then by a pump 15 tothe filter-press16 where the wax is removed as a dry dominantly crystalline cake. The'parafiin wax is dissolved in the petroleum lubricating oil with which it was simultaneously evolved from the successive rectification zones. It is cooled in thechiller 14 (in accordance with established practice) to a temperature at which "substantial quantities of crystalline-paraffin wax'areformed. It may, for example, be

'cooled to a temperature of 30 to 15 F. be-

fore pressing. .The yield of paraifin distillate viz, paraffin-bearing lubricating oil of good quality obtained directly and without cracking in this way will be equal to or greater than the total yield'of distillate representingthat out directly from the crude oil and that obtained from rerunning the unfit distillate, according to the prior processes. It will be in all respects of as good quality, containing the same percentage of viscous lubricating fractions and of wax. From the last still 3 a further quantity of paraffin distillate is secured which is of very high viscosity and contains a further quantity of paraflin wax, a separation of which can be effected by similar treatment.

' By our process, therefore, we obtain direct- 1y from the wax-bearing oil, such as paraffinbase crude oil, a full yield of paraffin distillate of a quality equal to that heretofore obtained only by resorting to cracking; but we obtain in addition an important additional yield of viscous parafiin distillate, which we believe to represent the constituents heretofore destroyed or sacrificed in order to obtain the quality and yield of the parafiin distillate previously obtainable. The additional paraflin distillate obtained by our process therefore represents a net gain of viscous lubricating oils and paraffin wax. The procedure used for further refining of this ad ditional distillate may be either that heretofore known and used for oils of generally similar properties, or it may be the same here described, or it may be a combination of these. I

Although the full advantage of the above invention can be realized only when cracking is reduced to a minimum, as by the use of a high vacuum, it will be understood that a considerable part of the benefit can be realized by adequate fractionation during a continuous distillation in which the reduction of the still temperatures and consequent reduction of cracking is accomplished-byv the use of relatively large quantities of steam.

We claim:' 1. The method of obtaining high yields. of

a pressable paraflin distillate from a paraflinbearing crude petroleum from which conrectifying the vapor under vacuum to produce an overhead vapor consisting of paraflin distillate, conducting away and condensing the vapor.

3. The method of obtaining high yields of a pressable par-aflin distillate from a paraflim bearing crude petroleum from which constituents of lower boiling point/than lubrieating oil have been substantially .removed, which comprises heating the crude oil to a temperature suflicient to cause vaporization, conducting the vapor to a group of fractionation zones in communication, each of which zones comprises liquid and vapor phases in partial equilibrium and under vacuum to produce a rectified vapor consisting of paraffin distillate.

4. Method according to claim 3 in which the vapor produced is conducted away, condensed, cooled to the point at which paraflin precipitates in crystalline form and filtered to produce a residue of paraflin wax and a filtrate of petroleum lubricating oil.

5. Method according to claim 3 in which the crude oil is heated to a temperature not ex- Cir ceeding 640 F.

6. Method according to claim 3 in which the crude oil is maintained during the heating under an absolute pressure of not exceedin 30 mm. of mercury.

. Method according to claim 3 in which the crude oil is heated to a temperature not exceeding 640 F. under anabsolute pressure not exceeding 30 mm. of mercury.

NATHANIEL E. LOOMIS. WARREN K. LEWIS. 

